In laying pipe, such as in gas or oil pipeline, it s conventional that lengths of pipe are supported end to end on stacked lumber pieces known as “skids” so that the pipe lengths can be held at a required height to be supported and aligned end to end for welding of the lengths, prior to feeding of the completed welded length into a trench adjacent to the stacks. After the pipe lengths are welded into a continuous length, the pipe is lifted from the skids and deposited in a continuous action along its length into the trench.
At some point, usually after the pipe has been laid into the trench, it is necessary to collect the lumber pieces from the skids and to transport them to a new site, preferably to be used again, for example at a further location along the pipeline.
The lumber pieces, which are conventionally either four or five feet in length and six by four inches in cross section are lifted and handled manually for stacking onto a transport container. This manual process is expensive and time consuming, since it requires a gang of laborers working hard and commanding high wages. In many cases the stack has been disturbed, and the pieces are strewn about, or even compressed in the ground by the tracks of passing vehicles, making the work even more labor intensive.
While this step is a relatively minor one in the process of laying the pipeline, it constitutes a significant expense and therefore provides a significant opportunity for a manufacturer of an effective machine which will carry out this step while eliminating or reducing the manual labor involved.
In U.S. Pat. No. 5,934,861 issued Aug. 10, 1999, which corresponds to Canadian patent application no. 2,241,682 published February 1999, discloses an apparatus for picking up pieces of lumber and conveying them to a transport truck. Canadian patent application no. 2,315,046 published Feb. 3, 2002 discloses an apparatus for picking up, stacking and bundling pieces of lumber.
Both of these prior art apparatuses are limited in application, in that they require smooth, flat and dry ground conditions in order to pick up lumber pieces from the ground. Further, they cannot pick up lumber pieces from a ground surface that is more than 30 cm above or below the tractor that is powering the apparatus. They are also limited in that the area in which lumber can be picked up is restricted to the width of the opening of the pick up section of the apparatus.